This work describes the segmentation of commercial crystalline silicon solar cells into smaller sections and their subsequent restructuring into interconnected arrays, based on an auxetic rotating-square architecture, to produce a lightweight, flexible and stretchable solar module. As expected, the sectioning of the solar cells reduces their power conversion efficiency due to increased carrier recombination at the sawn edges. However, average cell section efficiencies are shown to be less than 1.8% lower than the original cells. Output voltage and current can be tailored according to the combination of series or parallel connections between solar cell sections in the design. Due to the negative Poisson's ratio of the auxetic structure, bidirectional expansion with uniaxial stretching is achieved, opening gaps in the module, which allows the light transmittance to be adjusted. Mechanical tests reveal that the structures are robust to repeated cycles of expansion and relaxation, aided by the joint rotation mechanism of expansion that avoids excessive strain on the joint material. The modules are fully expanded when each cell section is rotated by 45 degrees. In this expanded state, modules made of 31.75 mm x 31.75 mm solar cell sections have a strain of 67% and transmittance of 41.9%. Modules incorporating the smaller 20 mm x 20 mm cell sections have a maximum strain of 60%, with a corresponding transmittance of 49.5%. A geometric model is used to show that by varying the design parameters, the transmittance maximum, minimum and range can be tuned, opening up various potential applications that include BIPV (e.g., partially shaded windows), AgriPV (e.g., greenhouse roofs), portable PV devices and wearables.

Feasibility software for photovoltaic (PV) systems leverage decomposition-transposition model pairs to approximate Plane-of-Array (POA) irradiance. This study analyses the accuracy of 15 optical model pairs, using minute input irradiance, to assess POA predictions in a temperate setting by comparing to measured POA for both a tracker and a 55 degrees south-facing tilted system. Using the Mean Absolute error (MAE) of <= 5% as the benchmark, variations were revealed across diverse sky conditions. Model estimates showcased a range of errors, from 2.67% to 51.07%, influenced by condition and system type. For the tracking system, the evaluation showed that in clear conditions, 10 pairs maintained errors within the range. However, this success diminished under intermediate skies, with 5 models remaining within range, and further reduced to 2 models in overcast conditions. The fixed-tilt system demonstrated similar trends but with fewer models meeting the required thresholds; 4 in clear and 2 in intermediate conditions. Only the DISC-SO model pair met the threshold in overcast conditions, exhibiting an MAE of 2.67%. Thus, DISC-SO made it a preferred choice for transposing horizontal irradiance. However, R2 values highlighted challenges due to the high temporal resolution of input data and the hourly data-based SO transposition model. Moreover, the study also examined the impact of decomposition and transposition models on percentage errors. Decomposition changes caused up to 2.43% for tracking systems and 5.34% for fixed-tilt systems. Transposition errors were higher, at 8.53% and 11.51%. Using hourly data reduced errors to 2.35%, 1.44%, and -2.15% in clear, intermediate, and overcast conditions.

Two-dimensional (2D) transition-metal dichalcogenides have shown great potential for energy storage applications owing to their interlayer spacing, large surface area-to-volume ratio, superior electrical properties, and chemical compatibility. Further, increasing the surface area of such materials can lead to enhanced electrical, chemical, and optical response for energy storage and generation applications. Vertical silicon nanowires (SiNWs), also known as black-Si, are an ideal substrate for 2D material growth to produce high surface-area heterostructures, owing to their ultrahigh aspect ratio. Achieving this using an industrially scalable method paves the way for next-generation energy storage devices, enabling them to enter commercialization. This work demonstrates large surface area, commercially scalable, hybrid MoS2/SiNW heterostructures, as confirmed by Raman spectroscopy, with high tunability of the MoS2 layers down to the monolayer scale and conformal MoS2 growth, parallel to the silicon nanowires, as verified by transmission electron microscopy (TEM). This has been achieved using a two-step atomic layer deposition (ALD) process, allowing MoS2 to be grown directly onto the silicon nanowires without any damage to the substrate. The ALD cycle number accurately defines the layer number from monolayer to bulk. Introducing an ALD alumina (Al2O3) interface at the MoS2/SiNW boundary results in enhanced MoS2 quality and uniformity, demonstrated by an order of magnitude reduction in the B/A exciton photoluminescence (PL) intensity ratio to 0.3 and a reduction of the corresponding layer number. This high-quality layered growth on alumina can be utilized in applications such as for interfacial layers in high-capacity batteries or for photocathodes for water splitting. The alumina-free 100 ALD cycle heterostructures demonstrated no diminishing quality effects, lending themselves well to applications that require direct electrical contact with silicon and benefit from more layers, such as electrodes for high-capacity ion batteries.

Reflectance measurements of thin films on glass are often taken at a single angle of incidence at or close to normal, which provides useful information but does not give a full picture of the coating/substrate performance for its intended application. In this work, variable angle reflectance (VAR) measurements are taken for glass substrates with and without anti-reflection (AR) coatings, using an angle-resolved spectrophotometer. Internal rear surface reflection is suppressed with the adhesion of a highly-absorbing black foil to the back of the samples. The technique allows reflectance measurements to be taken from incidence angles of 8 degrees to 80 degrees across a wavelength range of 400 - 1000 nm. The reflectance of all samples is generally seen to increase with increasing incidence angles above 40 degrees, and the effectiveness of the AR coatings varies, with multilayers being more effective below 40 degrees, and the single layer coating more effective above 40 degrees. VAR measurements of AR coatings are crucial in providing real-world performance data and predicting PV module performance across varying spectral conditions, and these data can guide further optimisation of AR coatings for PV applications.

Photovoltaics (PVs) are a critical technology for curbing growing levels of anthropogenic greenhouse gas emissions, and meeting increases in future demand for low-carbon electricity. In order to fulfill ambitions for net-zero carbon dioxide equivalent (CO _2 eq) emissions worldwide, the global cumulative capacity of solar PVs must increase by an order of magnitude from 0.9 TW _p in 2021 to 8.5 TW _p by 2050 according to the International Renewable Energy Agency, which is considered to be a highly conservative estimate. In 2020, the Henry Royce Institute brought together the UK PV community to discuss the critical technological and infrastructure challenges that need to be overcome to address the vast challenges in accelerating PV deployment. Herein, we examine the key developments in the global community, especially the progress made in the field since this earlier roadmap, bringing together experts primarily from the UK across the breadth of the PVs community. The focus is both on the challenges in improving the efficiency, stability and levelized cost of electricity of current technologies for utility-scale PVs, as well as the fundamental questions in novel technologies that can have a significant impact on emerging markets, such as indoor PVs, space PVs, and agrivoltaics. We discuss challenges in advanced metrology and computational tools, as well as the growing synergies between PVs and solar fuels, and offer a perspective on the environmental sustainability of the PV industry. Through this roadmap, we emphasize promising pathways forward in both the short- and long-term, and for communities working on technologies across a range of maturity levels to learn from each other.

Photovoltaics (PVs) are a critical technology for curbing growing levels of anthropogenic greenhouse gas emissions, and meeting increases in future demand for low-carbon electricity. In order to fulfil ambitions for net-zero carbon dioxide equivalent (CO2eq) emissions worldwide, the global cumulative capacity of solar PVs must increase by an order of magnitude from 0.9 TWp in 2021 to 8.5 TWp by 2050 according to the International Renewable Energy Agency, which is considered to be a highly conservative estimate. In 2020, the Henry Royce Institute brought together the UK PV community to discuss the critical technological and infrastructure challenges that need to be overcome to address the vast challenges in accelerating PV deployment. Herein, we examine the key developments in the global community, especially the progress made in the field since this earlier roadmap, bringing together experts primarily from the UK across the breadth of the photovoltaics community. The focus is both on the challenges in improving the efficiency, stability and levelized cost of electricity of current technologies for utility-scale PVs, as well as the fundamental questions in novel technologies that can have a significant impact on emerging markets, such as indoor PVs, space PVs, and agrivoltaics. We discuss challenges in advanced metrology and computational tools, as well as the growing synergies between PVs and solar fuels, and offer a perspective on the environmental sustainability of the PV industry. Through this roadmap, we emphasize promising pathways forward in both the short- and long-term, and for communities working on technologies across a range of maturity levels to learn from each other.

Black silicon nanotextures offer significant optical performance improvements when applied to crystalline silicon solar cells. Coupled with conventional pyramidal textures, to create so-called hybrid black silicon, these benefits are shown to be further enhanced. Presented here is a comprehensive analysis of different variations of this texture, coupled with typical anti-reflectance schemes such as coated pyramids, with a view to the significance of this on subsequent, real-world, solar energy generation. The study uses an angle-resolved spectrophometry system to characterise and compare the optical properties of these surface textures in terms of reflectance versus wavelength and incident angle, with and without encapsulant layers. This analysis, coupled with time-resolved, location specific irradiance data, leads to a new figure-of-merit, the weighted reflectivity, with which to compare surface textures for use in solar cells. Weighted reflectivity for an encapsulated solar cell surface, averaged over a year, for a Southampton, UK, location is calculated to be 7.6% for hybrid black silicon, compared to 10.6% for traditional random pyramids with a thin film anti-reflective coating.

Surface reflectance is a practical metric of the optical performance of a material. Applications, such as glass manufacturing, light sensing, satellite reflectors, and photovoltaics, depend on their reflectance properties and generalized optical performance. Reflectance measurements are rarely reported comprehensively, with only a single angle of incidence common in most datasets. Here, we present a new spectrophotometry system capable of performing angle-, wavelength-, and polarization-resolved reflectance measurements on various surfaces. Data from such a system yields significant information regarding the everyday, real-world performance of said materials. We perform exemplar studies by characterizing several standard thin-film antireflectance coatings and comparing the results to their known theoretical optical response. We also present results from measurements on an optical insulating material as well as a selection of wall paints to showcase the versatility of the technique. We highlight the parallels between measurement and theory, while analyzing the realistic implications of the measurements on their respective material’s practical performance under real-world conditions.

Black silicon (b-Si) has been widely investigated as a potential replacement for more traditional antireflective schemes for silicon solar cells, such as random pyramids, due to its reduced broadband reflectance and improved light-trapping properties. Wavelength and angle resolved scattering (WARS) reflectance measurements provide the means of analysing the amount of light scattered from a textured surface, which can be of interest when considering the amount of light trapped through total internal reflectance (TIR) at various interfaces in an encapsulated photovoltaic module. Here we present and analyse results from WARS measurements on b-Si surfaces fabricated using metal assisted chemical etching (MACE). Large angle scattering is observed for the entire spectrum, increasingly so for shorter incident wavelengths and increasing height of texture features. This is predicted to result in 35–40% of the reflected light being trapped by TIR at the glass-air interface and redirected back onto the sample, when the sample is encapsulated in standard PV module materials. This leads to a calculated additional boost of up to 0.45% in the photogenerated current of an encapsulated black silicon solar cell. This exceeds the calculated 0.21% boost due to TIR predicted for an encapsulated solar cell employing the industry-standard random pyramid texture with a thin film antireflective coating.

The development of patterning materials ("resists") at the nanoscale involves two distinct trends: one is toward high sensitivity and resolution for miniaturization, the other aims at functionalization of the resists to realize bottom-up construction of distinct nanoarchitectures. Patterning of carbon nanostructures, a seemingly ideal application for organic functional resists, has been highly reliant on complicated pattern transfer processes because of a lack of patternable precursors. Herein, we present a fullerene-metal coordination complex as a fabrication material for direct functional patterning of sub-10 nm metal-containing carbon structures. The attachment of one platinum atom per fullerene molecule not only leads to significant improvement of sensitivity and resolution but also enables stable atomic dispersion of the platinum ions within the carbon matrix, which may gain fundamentally new interest in functional patterning of hierarchical carbon nanostructures.

Highly passivating, hole selective contacts are required for future high efficiency silicon solar cells. This work investigates selected dielectrics as potential SiOx replacements to act as hole selective contacts. AlOx and SiNx were identified as good candidates due to their low valence band offsets to silicon and proven surface passivation capabilities. Simulated J-V curves show AlOx and SiNx maintain acceptable contact resistivities at thicknesses below 1.4 and 1.7 nm, respectively. The SiOx hole contact was found to become extremely resistive even at thicknesses <1 nm, suggesting that either pinholes dominate conduction, or the band offset parameters differ from those in real TOPCon structures. The passivation of the dielectrics was also simulated, with SiOx outperforming both AlOx and SiNx primarily due to the excellent interface. Additionally, the effect of nanolayer built in charge was investigated. Charges below 1012 q/cm2 were found to have little effect, while negative charges above 1012 q/cm2 resulted in reductions in the contact resistivity and recombination current. The calculated selectivity for a 1.4 nm layer of AlOx was 12.9, while a value of 13.8 was calculated for SiNx at typical intrinsic charge levels.

Solar cells based on GaAs often include a wide-bandgap semiconductor as a window layer to improve surface passivation. Such devices often have poor photon-to-electron conversion efficiency at higher photon energies due to parasitic absorption. In this article, we deposit FAPbBr3 perovskite quantum dots on the AlInP window layer of a GaAs thin-film solar cell to improve the external quantum efficiency (EQE) across its entire absorption range, resulting in an 18% relative enhancement of the short-circuit current density. Luminescent downshifting from the quantum dots to the GaAs device contributes to a large effective enhancement of the internal quantum efficiency (IQE) at shorter wavelengths. Additionally, improved surface passivation of the window layer results in a 14–16% broadband increase of the IQE. These mechanisms combined with increased overall photon collection (antireflective effects) results in a doubling of the EQE in the ultraviolet region of the solar spectrum. Our results show a promising application of perovskite nanocrystals to improve the performance of well-established thin-film solar cell technologies.

Reduction of surface reflection loss is crucial for high efficiency next generation Si solar cells. Surface texturing provides a viable method to reduce loss over the full solar bandwidth. Previous studies have concentrated on simple moth-eye silicon pillar arrays protruding from the surface. Using FDTD simulation methods, we undertake a systematic investigation into performance benefits provided by complex semi-random photonic quasi-crystal surface patterning methodologies whereby arrays of air holes are etched deep into the solar cell surface. In contrast to other studies we carefully investigate the effect of lattice symmetry, systematically comparing performance of simple 6-fold symmetric triangular photonic crystal patterning to 12 fold symmetry photonic quasicrystal patterning and infinitely symmetric 2D Fibonacci patterning. We optimize key geometric parameters such as lattice pitch, hole size and etch depth to maximize optical performance for each lattice type. 12 fold photonic quasi crystal lattice is found to provide best overall anti-reflectance performance providing a solarcorrected average reflectance of 8.3% for a hole depth of 1.5 mu m and 300 nm diameter, in comparison to 36.4% for a bare silicon solar cell surface. Practical feasibility of the optimal designs is demonstrated by fabrication of physical prototypes consisting of arrays of nm scale air-holes etched into the surface of a silicon slab fabricated Using e-beam lithography and ICP/RIE etching. FDTD Simulation methodology is validated by convergence studies as well as comparison to optical measurements on these fabricated devices. Furthermore, in contrast to previous studies we provide an in depth analysis of the physical mechanisms responsible for reduction in surface reflection, determining the parameter space where conventional Gaussian optical processes such as effective refractive index, refraction and Fresnel reflection dominate, vs parameter space where sub wavelength photonic crystal scattering effects play the main role. We finish up with an analysis of electrical performance for the optimal designs to further validate real world performance. Taking electrical performance into account we determine that infinite-symmetry 2D Fibonacci patterning far outperforms lower symmetry 12 fold and triangular arrangement. We believe that this is the first in depth investigation into 2D Fibonacci patterning in silicon solar cells.

Wavelength and angle resolved scattering (WARS) reflectance measurements are attractive to the photovoltaic (PV) industry as a means of characterizing the light-trapping properties of a textured front surface. Moreover, at the PV module level, where a stack comprising encapsulants and glass is present, large angle scattering can promote total internal reflection at the interfaces and redirect light back towards the solar cell, thus increasing the photocurrent of the device. In this work, we present WARS measurements of a potassium hydroxide (KOH)etched random pyramid surface in the 6 degrees-90 degrees range and identify the main paths the photons experience through reflections from various facets of the pyramids. Our results, combined with ray-tracing predictions, show that a reassessment of the morphology for simulation inputs is advised for a more comprehensive description of the experimental light paths due to a distribution of power across multiple scattering angles and a lower average pyramid base angle. In addition, we discuss the implications on the total amount of light trapped at the glass-air interface and show that for a typical encapsulant refractive index of 1.5, approximately 14.5% of the scattered light is predicted to be trapped by the fabricated pyramidal texture. This is a significant increase over the 3.8% calculated to be trapped when assuming a dihedral base angle fixed to 54.74 degrees.

As the era of microscale technologies becomes increasingly overcome by that of the nanoscale, an ever-increasing emphasis on the accurate modelling of such scaled systems is apparent. This work explores the combination of the finite element method with a new set of statistical algorithms to model the optical properties of disordered nanoscale morphologies. A silicon surface textured with a random distribution of nanowires is created to simulate, as an example study, how it responds to incident light. By averaging over many iterations of the model in which the structural parameters are varied around average values, a good match to experiment is achieved, showcasing an error as low as 1.34% in magnitude against measured data. This research introduces a fresh computational approach to simulating heterogeneous material structures widely applicable for modelling across the field of nanotechnology.

Fully exploiting the power conversion efficiency limit of silicon solar cells requires the use of passivating contacts that minimize electrical losses at metal/silicon interfaces. An efficient hole-selective passivating contact remains one of the key challenges for this technology to be deployed industrially and to pave the way for adoption in tandem configurations. Here, we report the first account of silicon nitride (SiNx) nanolayers with electronic properties suitable for effective hole-selective contacts. We use x-ray photoemission methods to investigate ultra-thin SiNx grown via atomic layer deposition, and we find that the band alignment determined at the SiNx/Si interface favors hole transport. A band offset ratio, ΔEC/ΔEV, of 1.62 ± 0.24 is found at the SiNx/Si interface for the as-grown films. This equates to a 500-fold increase in tunneling selectivity for holes over electrons, for a film thickness of 3 nm. However, the thickness of such films increases by 2 Å–5 Å within 48 h in cleanroom conditions, which leads to a reduction in hole-selectivity. X-ray photoelectron spectroscopy depth profiling has shown this film growth to be linked to oxidation, and furthermore, it alters the ΔEC/ΔEV ratio to 1.22 ± 0.18. The SiNx/Si interface band alignment makes SiNx nanolayers a promising architecture to achieve widely sought hole-selective passivating contacts for high efficiency silicon solar cells.

Reported here is the development of a broadband, angular-resolved and polarised hemispherical reflectometer. Such devices are able to provide succinct and meticulous data regarding the optical response characteristics of a given surface. We investigate such characteristics of a variety of materials featuring surface texturing and report a comprehensive analysis of the data returned. Our findings demonstrate the key role played by both the micro- and nano-scale features of a given surface topology on the wide-angle anti-reflectance properties of that surface.

Hot wire chemical vapour deposition (HWCVD) is explored as a way of growing boron-doped silicon for photovoltaic devices. Deposition temperatures are measured using a custom-built monitoring system for two different filament configurations within the HWCVD tool. A refined fabrication process is presented, using an altered filament arrangement, that currently provides a maximum deposition temperature of 535 degrees C, for growing boron-doped silicon films via HWCVD, with the inclusion of a short post-deposition anneal at 800 degrees C for 2 min. Transmission electron microscopy reveals improvements in interfacial quality, as well as larger grains, present after post-annealing treatments. In addition, re-crystallisation of as-deposited amorphous Si films under a short anneal is confirmed using Raman spectroscopy. The enhancements in morphology translate to a boost in current rectification based on dark current-voltage measurements. This is further supported by secondary-ion mass spectrometry analysis, presenting p(+) properties with uniform doping in the 10(21) cm(-3) region.

Compact vortex beam emitters have emerged as new light sources for novel applications in areas including spectroscopy, particle manipulation, and communications. Reported devices depend on linear optical phenomena and emit light in the near-infrared (IR) regime. Here, we propose and numerically evaluate a nonlinear vortex beam emitter that functions in the THz regime. The design utilizes a LiNbO3 microring, a Si microdisk, and an Au second-order top grating to convert waveguide-coupled IR light into a freely propagating THz beam via a difference-frequency generation. The output beam carries a topological charge that is tunable with input wavelengths. Three devices are evaluated in a test frequency range from 9 THz to 13.5 THz, and the topological charge can change from −2 to 4. A frequency shift accompanies the change in the topological charge, and its magnitude depends on the planar dimensions of the emitter.